The present invention relates to an end point quality control light circuit designed for specific use with a water purifier, or demineralizer, unit. Yet the inventive circuit finds application wherever the quality of an effluent is important.
A demineralizer unit is disclosed in U.S. Pat. No. 3,245,537; this unit includes an integral end point quality control light. An improved, screw-in end point quality control light unit can be seen in U.S. Pat. No. 3,334,745. Each of these patents is owned by the present assignee. In the latter of these known end point lights, a neon bulb, two resistors, a pair of probes, and power wires for bringing standard household current to the bulb and probes are encapsulated in a common housing. The housing is externally threaded to enable association with mating threads of the demineralizer unit's discharge spout. The probes reside in the discharge path of the water, and are excited by approximately 60 volts A.C.; water quality is indicated by the state of the neon bulb.
This known end point quality control device is quite effective. However, recently enacted and expected codes, setting stringent requirements for electrical and electronic measuring and control instrumentation, indicate the possible need for redesign of such a device. As an example, the attention of the reader is directed to the American National Standard, Safety Requirements for Electrical and Electronic Measuring and Controlling Instrumentation (the ANSI Code), ANSI C39.5-1974. This code specifies safety requirements for devices such as end point quality control lights, and sets maximum permissible limits for electrical parameters such as insulation breakdown (2500v.) and leakage current (0.5ma). In this latter regard, a code enacted by the city of Los Angeles limits leakage current to 0.005ma for medical devices.
It is toward the development of an end point quality control light circuit capable of meeting the most stringent codes, that the present invention is directed.